1. Field of the Invention
The invention concerns electronic messaging in general and electronic mail in particular.
2. Description of the Prior Art
A major annoyance in the conventional mail system is junk mail. As electronic mail has grown in availability and popularity, junk electronic mail has become a problem as well. Indeed, the ease with which an e-mail message may be sent to many recipients may eventually make junk e-mail an even worse problem that junk conventional mail.
The prior art has attempted to deal with the junk e-mail problem by means of mail filters in an e-mail recipient's local e-mail system. Such a filter sorts incoming e-mail for the recipient into categories determined by the recipient. The filter simply scans each e-mail message as it reaches the recipient and determines what category it should be placed in. One category is of course "discard". Messages which the filter places in that category are automatically discarded. Prior-art filters have had varying degrees of intelligence; some have simply worked with lists of source addresses and have sorted according to the source of the message; others have used keywords provided by the recipient to sort; with others, finally, the filter observes how the recipient sorts his e-mail for awhile and is then able to sort in a similar fashion. For details about mail filters, see Peter W. Foltz and Susan T. Dumais, "Personalized information delivery: an analysis of information filtering methods", Communications of the ACM, vol. 35, no. 12, Dec., 1992, pp. 51-60; D. K. Gifford, R. W. Baldwin, S. T. Berlin, J. M. Lucassen, "An architecture for large scale information systems", in Proceedings Tenth Symposium on Operating Systems Principles, (Orcas Island, Wash., Dec 1985), pp. 161-170; E. Lutz, H. V. Kleist-Retzow, and K. Hoerning, "MAFIA--An active mail-filter agent for an intelligent document processing support", in Multi-User Interfaces and Applications, S. Gibbs andn A. A. Verrijn-Stuart, Eds, North Holland, 1990, pp. 16-32; T. W. Malone, K. R. Grant, F. A. Turbak, S. A. Browst, M. D. Cohen, "Intelligent information sharing systems", Commun. ACM 30, 5 (May 1987) 390-402; S. Pollack, "A rule-based message filtering system", ACM Trans. Off. Inf. Syst. 6, 3 (July 1988), 232-254. P. Maes, "Agents that Reduce Work and Information Overload", Commun. ACM 37 (7) (July 1994), pp. 31-40. A problem with all such filters is that sorting for another person is difficult even for a human being, and if a filter is going to be useful, it cannot do much worse than a human would.
One of the reasons for the junk mail is that present-day e-mail systems require that recipients be addressed by e-mail addresses. In order to ensure that an e-mail message will reach everyone who might possibly be interested in it, the sender typically uses a list of addresses which includes those who might be interested but includes many others as well. For everyone but those actually interested, the e-mail is of course junk mail.
What is needed to reduce the amount of junk mail is a technique which permits a sender to use something in addition to the e-mail address to specify the kinds of people who are to actually receive the e-mail and permits a filter to use the information provided by the sender to filter the mail so that only those kinds of people actually receive it. It is an object of the invention disclosed herein to provide such a technique and thereby to reduce the amount of junk e-mail received by a user of the e-mail system.